As conventional shock absorber fluids there are known, for example, those employing poly-α-olefins, esters, silicone oils or deep dewaxed base oils. It has also been attempted to improve the properties of conventional shock absorber fluids by addition of various additives (for example, Patent documents 1-9).    [Patent document 1] Japanese Unexamined Patent Publication HEI No. 3-285989    [Patent document 2] Japanese Unexamined Patent Publication HEI No. 5-86390    [Patent document 3] Japanese Unexamined Patent Publication HEI No. 5-247482    [Patent document 4] Japanese Unexamined Patent Publication HEI No. 6-220480    [Patent document 5] Japanese Unexamined Patent Publication No. 2000-119672    [Patent document 6] Japanese Unexamined Patent Publication No. 2000-044971    [Patent document 7] Japanese Unexamined Patent Publication No. 2000-109876    [Patent document 8] Japanese Unexamined Patent Publication No. 2000-119672    [Patent document 9] Japanese Unexamined Patent Publication No. 2005-314609